1. Field of the Invention
The present invention relates to a wire dot printer head of wire dot printer, and more particularly, to a structure where magnetic resistance between an armature and a yoke is reduced.
2. Discussion of the Background
Conventionally, known is a wire dot printer head, in which a coil is attached to a core magnetically coupled to a yoke and an armature to drive a wire is provided capable of approaching/separating to/from the core. Printing is performed by driving the armature by feeding a current through the coil and colliding the wire against a print sheet by driving energy of the armature.
The requirement for armature performance is to reduce weight for high speed operation while have a function of forming a magnetic circuit to the yoke and the core and a function of driving the wire. This requirement for the armature is met by constructing the armature by coupling a magnetic circuit formation member for forming a magnetic circuit with respect to the yoke and the core to a light-weight and high-strength arm, and by coupling the wire to an end of the wire.
As usage of the armature comprised of the magnetic circuit formation member and the arm, if the portion of the magnetic circuit formation member is simply provided to be opposed to end surfaces of the core and the yoke, it is structurally difficult to increase opposing surface areas of the magnetic circuit formation member and the yoke. As a result, magnetic resistance between the magnetic circuit formation member and the yoke increases, and the speed of response operation of the armature when a current is fed through the coil is lowered.
Japanese Laid-Open Publication No. Hei 5-238019 discloses an armature constructed by coupling a magnetic material for formation of a magnetic circuit with respect to the yoke and arm to a light-weight and high-strength arm. In this Japanese Laid-Open Publication No. Hei 5-238019, a projecting coupling member having a half-round cross section is formed in a magnetic path portion of the armature, the coupling member is engaged in a recess-shaped rotation support member formed in a part of the yoke, and the armature is rotated about the rotation support member.
However, as apparent from Japanese Laid-Open Publication No. Hei 5-238019, the projecting coupling member formed in the magnetic path portion of the armature and the recess-shaped rotation support member formed in the yoke have mutually opposing surfaces in contact with each other. There is no idea of feeding a magnetic flux between an inner surface of the recess-shaped rotation support member and an outer surface of the coupling member of the armature.
Accordingly, an object of the present invention is to realize a light-weight and high-strength arm to drive the wire, and especially to reduce the magnetic resistance between the magnetic circuit formation member, coupled to the arm to construct the armature, and the yoke.
The object of the present invention is attained by a novel wire dot printer head of the present invention.
Thus, according to the novel wire dot printer head of the present invention, as an armature is formed by coupling a magnetic circuit formation member having a supported piece with its one end inserted into a cavity formed on the surface of the yoke to an arm coupled to a wire, and the supported piece of the armature is rotatably supported by a support member, and a gap between a side surface of the cavity and a side surface of the supported piece, and a gap between a bottom surface of the cavity and an end surface of the supported piece can be maintained in status of constant proximity. Accordingly, the magnetic resistance between the magnetic circuit formation member and the yoke can be reduced.